The 'hyco-https' Package for Azure Relay Hybrid Connections

Overview

This Node package for Azure Relay Hybrid Connections is built on and extends the core 'https' Node module. This module re-exports all exports of that base module and adds new exports that enable integration with the Azure Relay service's Hybrid Connections HTTP request feature.

Existing applications that require('https') can use this package instead with require('hyco-https'). This allows an application residing anywhere to accept HTTPS requests via a public endpoint.

Documentation

The API follows the exact patterns of the Node 'http' and 'https' modules, and this document describes how this package differs from that baseline.

The module completely overrides the server behavior of the 'https' package, meaning that the same Node application instance cannot concurrently use the regular 'https' module functionality to listen locally for HTTP requests.

The client functionality of the 'https' package is untouched.

For application frameworks, such as ExpressJS, that internally override the https.ServerResponse class, the application should explicitly include the 'http' and 'hyco-https' modules in the following way, and before loading the framework, even if the framework commonly does not require a prior explicit reference of 'http' or 'https':

var http = require('http');
var https = require('hyco-https');
http.ServerResponse = https.ServerResponse;

var express = require('express');

Package Helper methods

There are several utility methods available on the package export that can be referenced like this:

const https = require('hyco-https');

var listenUri = https.createRelayListenUri('namespace.servicebus.windows.net', 'path');
listenUri = https.appendRelayToken(listenUri, 'ruleName', '...key...')
...

The helper methods are for use with this package, but might be also be used by a Node server for enabling web or device clients to create listeners or senders by handing them URIs that already embed short-lived tokens and that can be used with common WebSocket stacks that do not support setting HTTP headers for the WebSocket handshake. Embedding authorization tokens into the URI is primarily supported for those library-external usage scenarios.

createRelayListenUri

var uri = createRelayListenUri([namespaceName], [path], [[token]], [[id]])

Creates a valid Azure Relay Hybrid Connection listener URI for the given namespace and path. This URI can then be used with the createRelayedServer function.

• namespaceName (required) - the domain-qualified name of the Azure Relay namespace to use
• path (required) - the name of an existing Azure Relay Hybrid Connection in that namespace
• token (optional) - a previously issued Relay access token that shall be embedded in the listener URI (see below)
• id (optional) - a tracking identifier that allows end-to-end diagnostics tracking of requests

The token value is optional and should only be used when it is not possible to send HTTP headers along with the WebSocket handshake as it is the case with the W3C WebSocket stack.

createRelayHttpsUri

var uri = createRelayHttpsUri([namespaceName], [path], [[token]], [[id]])

Creates a valid Azure Relay Hybrid Connection HTTPS URI for the given namespace and path. This URI can be used with any HTTPS client.

• namespaceName (required) - the domain-qualified name of the Azure Relay namespace to use
• path (required) - the name of an existing Azure Relay Hybrid Connection in that namespace
• token (optional) - a previously issued Relay access token that shall be embedded in the send URI (see below)
• id (optional) - a tracking identifier that allows end-to-end diagnostics tracking of requests

The token value is optional and should only be used when it is not possible to send HTTP headers along with the WebSocket handshake as it is the case with the W3C WebSocket stack.

createRelayToken

var token = createRelayToken([uri], [ruleName], [key], [[expirationSeconds]])

Creates an Azure Relay Shared Access Signature (SAS) token for the given target URI, SAS rule, and SAS rule key that is valid for the given number of seconds or for an hour from the current instant if the expiry argunent is omitted.

• uri (required) - the URI for which the token is to be issued. The URI will be normalized to using the http scheme and query string information will be stripped.
• ruleName (required) - SAS rule name either for the entity represented by the given URI or for the namespace represented by teh URI host-portion.
• key (required) - valid key for the SAS rule.
• expirationSeconds (optional) - the number of seconds until the generated token should expire. The default is 1 hour (3600) if not specified.

The issued token will confer the rights associated with the chosen SAS rule for the chosen duration.

appendRelayToken

var uri = appendRelayToken([uri], [ruleName], [key], [[expirationSeconds]])

This method is functionally equivalent to the createRelayToken method above, but returns the token correctly appended to the input URI.

createRelayedServer

The createRelayedServer() method creates a server that does not listen on the local network, but delegates listening to the Azure Relay. Except for the options, it behaves just like the regular createServer() function.

Example

The sample included in this repo illustrates the use. For information on how to create an Hybrid Connection and obtain keys, please read through the Getting Started document.

If you are familiar with the regular 'https' module, you will find the code below just as familiar. Request and response and error handling is identical.

    const https = require('hyco-https');

    var args = { 
        ns : process.env.SB_HC_NAMESPACE, // fully qualified relay namespace
        path : process.env.SB_HC_PATH, // path of the Hybrid Connection
        keyrule : process.env.SB_HC_KEYRULE, // name of a SAS rule
        key : process.env.SB_HC_KEY // key of the SAS rule
    };
    
    var uri = https.createRelayListenUri(args.ns, args.path);
    var server = https.createRelayedServer(
        {
            server : uri,
            token : () => https.createRelayToken(uri, args.keyrule, args.key)
        },
        (req, res) => {
            console.log('request accepted: ' + req.method + ' on ' + req.url);
            res.setHeader('Content-Type', 'text/html');
            res.end('<html><head><title>Hey!</title></head><body>Relayed Node.js Server!</body></html>');
        });

    server.listen( (err) => {
            if (err) {
              return console.log('something bad happened', err)
            }          
            console.log(`server is listening`)
          });

    server.on('error', (err) => {
        console.log('error: ' + err);
    });

The options element supports a different set of arguments than the createServer() since it is neither a standalone listener nor embeddable into an existing HTTP listener framework. There are also fewer options available since the listener management is largely delegated to the Relay service.

Constructor arguments:

• server (required) - the fully qualified URI for a Hybrid Connection name on which to listen, usually constructed with the https.createRelayListenUri() helper.
• token (required) - this argument either holds a previously issued token string or a callback function that can be called to obtain such a token string. The callback option is preferred as it allows token renewal.